1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type magnetic transducer and a method of manufacturing the thin-film magnetic head.
2. Description of the Related Art
Thin-film magnetic heads have been widely used in hard disk drives used for computers and so on. Composite thin-film magnetic heads in particular have been widely used. A composite thin-film magnetic head is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
An induction-type magnetic transducer has two magnetic layers and a thin-film coil placed between the magnetic layers. The magnetic layers include magnetic pole portions opposed to each other with a gap layer in between. The pole portions are placed on a side of end faces of the magnetic layers facing toward a recording medium. The magnetic layers are magnetically coupled to each other on the other side.
With an increase in recording density of a hard disk drive used for computers and so on, the maximum frequency of data recorded or reproduced through the use of a thin-film magnetic head has reached a frequency as high as 100 MHz or above. In the case of an extremely high-speed hard disk drive, in particular, the maximum frequency of data to write has reached the order of 200 MHz. If the frequency of data to write increases, eddy current loss increases in the magnetic layers of an induction-type magnetic transducer. Accordingly, the following problems of reductions in properties have arisen: a reduction in intensity of a write magnetic field generated from the pole portions opposed to each other with the gap layer in between; an increase in delay between a write current (a current responsive to data to write) supplied to the coil and generation of a write magnetic field; and a decrease in gradient of rise of a write magnetic field with respect to time.
In order to suppress such eddy current loss, measures have been devised in related art, such as reducing a magnetic path length, that is, the length of the magnetic path made up of the magnetic layers between the medium-facing-surface-side end and the other end, or using a magnetic material with a high resistivity for the magnetic layers.
To improve recording density, it is desired that track density is increased. In Japanese Patent Application Laid-open Hei 8-87717 (1996), a thin-film magnetic head is disclosed for increasing track density. In the head an end of an insulating layer on which a thin-film coil is formed is placed at least 3 .mu.m away from the zero throat height position (the position of the medium-facing-surface-side end of an insulating layer that defines the throat height) toward the rear gap (portions of two magnetic layers in contact with each other). In the head the start point of the thin-film coil may be placed at least 10 .mu.m away from the zero throat height position. In the invention the throat height is the length (height) between the medium-facing-surface-side end of the pole portion and the other end. The throat height is also the length (height) between the medium facing surface and the medium-facing surface-side end of the insulating layer electrically isolating the thin-film coil.
However, the magnetic path length is not reduced in such a structure. It is therefore difficult to sufficiently increase the intensity of a write magnetic field or the gradient of rise of a write magnetic field with respect to time when the frequency of data to write increases.